Enable -Werror in Travis

AMDmi3 · AMDmi3 · commit d551c68a7461 · 2018-07-08T12:41:41.000+03:00
diff --git a/.travis.yml b/.travis.yml
@@ -25,7 +25,7 @@ script:
 - |-
   # Build hyperrogue.
   autoreconf -vi
-  ./configure
+  ./configure CXXFLAGS="-Wall -Werror -Wno-error=unused-result"
   make
 - |-
   # Test hyperrogue.
